CVE-2024-43796

express vulnerable to XSS via response.redirect()

Workarounds

users are encouraged to upgrade to the patched version of express, but otherwise can workaround this issue by making sure any untrusted inputs are safe, ideally by validating them against an explicit allowlist

Details

successful exploitation of this vector requires the following:

1. The attacker MUST control the input to response.redirect()
2. express MUST NOT redirect before the template appears
3. the browser MUST NOT complete redirection before:
4. the user MUST click on the link in the template

In express <4.20.0, passing untrusted user input - even after sanitizing it - to response.redirect() may execute untrusted code

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2024-43796 has a CVSS score of 5.0 (Low). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.20.0, 5.0.0); upgrading removes the vulnerable code path.

Kodem intelligence

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this issue is patched in express 4.20.0

1. What is CVE-2024-43796? CVE-2024-43796 is a low-severity cross-site scripting (XSS) vulnerability in express (npm), affecting versions < 4.20.0. It is fixed in 4.20.0, 5.0.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2024-43796? CVE-2024-43796 has a CVSS score of 5.0 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of express are affected by CVE-2024-43796? express (npm) versions < 4.20.0 is affected.
4. Is there a fix for CVE-2024-43796? Yes. CVE-2024-43796 is fixed in 4.20.0, 5.0.0. Upgrade to this version or later.
5. Is CVE-2024-43796 exploitable, and should I be worried? Whether CVE-2024-43796 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2024-43796 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2024-43796?
   • Upgrade express to 4.20.0 or later
   • Upgrade express to 5.0.0 or later

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